The present invention relates to a ceramic fiber product and system for high temperature, severe application environmental conditions, for example, a refractory, and which provides enhanced fiber properties and airborne fiber free installations. More particularly, the invention relates to a refractory insulation product and method for making the same that allows ceramic fiber to be used in higher temperature, more severe application environments than present standard ceramic fiber materials. The invention also relates to a structure using the ceramic fiber product, for example, a monolithic refractory lined structure for steel or ceramic foundries or other high temperature applications.
Virgin ceramic fiber is an excellent insulating material but has some drawbacks. For example, it has the tendency to shrink at elevated temperatures and in impurity laden environments, which limits its use in high temperature, severe application environments. Furthermore, there are limitations on the level of alumina or other refractory oxides or chemical compositions which can be achieved in conventional melt extracted ceramic fiber systems.
Densification and compression of ceramic fiber materials have been used in the past to improve performance of ceramic fibers at elevated temperatures. A disadvantage of these techniques has been that in order to achieve the higher densities and compressions required, the ceramic fiber blanket has to be subjected to forces supplied by mechanical or hydraulic jacks or presses, which are costly, require considerable amounts of time to operate and may be dangerous to person and property. In many cases, the higher densities and compressions are not enough to overcome the environmental conditions, and other methods including surface treatments of the ceramic fibers with ceramic coatings, after fabrication, into a structure, have been used with only limited success.
Applicants are aware of the following patents relating to the field of the invention:
______________________________________ U.S. Pat. No. Inventor ______________________________________ 1,870,094 Carlin 2,681,870 Novak 2,683,305 Goetzel 3,045,316 Gilbert 3,112,219 Politzer et al. 3,509,020 Gelsomino 4,040,847 Miiller 4,208,230 Magarian 4,369,203 Hansen 4,698,319 Ray 4,961,989 Grimwood 5,021,369 Ackerman et al. ______________________________________
U.S. Pat. No. 1,870,094 relates to a process of rendering a slag wool or mineral wool dustless, thereby reducing the danger of injury to workmen. The process comprises saturating the wool material with a solution, then removing the excess solution and drying the wool material. The solutions taught therein are other than water, for example, deliquescent salt or calcium chloride.
U.S. Pat. No. 3,045,316 relates to the formation of pads or blanks of mineral wool and to a method and apparatus for imparting predetermined surface configurations to the pads or blankets to facilitate application of the pads or blankets to surfaces to be protected thereby.
U.S. Pat. No. 3,509,020 relates to a method of bonding a plurality of laminated fibrous plies into an integral fiber sheet which is resistant to delamination during handling and/or use. The method incorporates interlocking the plies by applying an aqueous solution of a water soluble thickening agent to the surfaces of the individual fibrous plies and then pressing them together.
U.S. Pat. No. 4,040,847 relates to a refractory fiber thermal insulation composition suitable for use in water containing packages known as "wet packs". The reference teaches impregnating a refractory fiber blanket with a binder system comprising three basic components: an aqueous suspension of colloidal silica of critical particle size, ethylene glycol and water. The binder system is formed by mixing together the aqueous suspension of colloidal silica, ethylene glycol and added water. The mixture may be placed in a large vessel or tank into which the refractory fiber blanket is dipped. Alternatively, the patent states that the binder system may be pumped from a reservoir tank and sprayed onto the blanket. The impregnated blanket may then immediately be packaged in air and water-tight containers, preferably plastic bags. It is recommended that the blanket be first compressed by passing it through compression rolls to squeeze out the excess binder and accurately set the thickness of the blanket prior to packaging in the air and water-tight containers.
U.S. Pat. No. 4,208,230 relates to an apparatus and method for impregnating a fibrous web with liquid resin. A moving, fibrous web is impregnated with the resin by applying the resin on the surface of the web, spreading the resin over the web surface, pressurizing a portion of the resin into the web to partially saturate the web with the resin and leave residual resin on the web, and metering the residual resin into a layer of substantially uniform thickness. This layer is then forced into the web to saturate it with the resin. The patent discloses that the method is particularly effective for producing plastic pipe incorporating at least one layer of fibrous material saturated with liquid resin.
U.S. Pat. No. 4,369,203 relates to a process for the impregnation of asbestos or other fibrous materials, comprising, as a first step, impregnating, with 10 the application of pressure, the material with a polymeric resin binder to saturate substantially the material with the binder and, as a second binder gel step, applying a polymeric resin compound comprising a polymeric resin and a filler. This process was designed to prevent the escape of minute fibers of asbestos into the atmosphere to reduce the health hazard associated with asbestos. A roller can be used to compress the asbestos material to cause movement of the liquid to penetrate entirely through the material.
U.S. Pat. No. 4,961,989 relates to a flame-resisting material consisting of layers of ceramic fibers imbedded with a silicone rubber compound. A ceramic fiber cloth is cut into a predetermined size and laid horizontally on a polished lower platen. A silicone rubber compound is then applied to the upper face of the cloth. The cloth is then turned over and the upper side is rolled with a roller to squeeze the silicone rubber compound through the interstices of the cloth weave.
U.S. Pat. No. 5,021,369 relates to a process of gelling a sol in fiber-formed ceramic insulation. The patent details a process in which a felted mat of ceramic fibers is impregnated with a sol-gel glass binder and is exposed to a low voltage direct current to catalytically gel the binder at ambient temperature and ambient pressure without Ph conversion catalysts. The gelled binder can be converted to a ceramic thereafter and is stabilized by firing above 525.degree. F.
Nothing in the prior art, of which applicants are aware, teaches or suggests a method for impregnating a ceramic fiber blanket with water or a nonbinding aqueous solution and compressing the blanket with a roller or other compressing means, which results in the manufacture of a highly dense and highly compressed ceramic fiber blanket which can be used in higher temperature, more severe application environments than present standard ceramic fiber systems.